1. Field of the Invention
The invention relates to private telephone networks and more particularly to real time services in interchange units of private telephone networks.
2. Description of the Prior Art
From the functional point of view, a private network interchange unit, for example the AS 4000 interchange unit supplied by the assignees of the inventors, has two separate parts. A first part of the interchange unit provides real time services and another part provides mixed mode services. The real time services are in particular services related to the transmission of calls in progress. The mixed mode services are used by machines or applications for which real time operation is not indispensable. These include call routing, specific charge metering and traffic analysis services.
Using a specific protocol for the dialog between interchange units in real time, for example the ABCF protocol, which is a multi-manufacturer protocol, used by the assignees of the inventors in particular but also by other manufacturers, is also known in the art. Another open protocol used for real time dialog between private network interchange units is the QSIG protocol, details of which can be found in ETS standard 300172.
FIG. 1 is a diagrammatic representation of two interchange units and the system elements needed to support dialog between them. As explained above, each of the interchange units 2 and 10 has a real time part 4 or 12 and a mixed mode part 6 or 14. The real time part of each interchange unit includes a line circuit 8 or 16. Each line circuit separates the interchange unit from a line 18. The two line circuits are connected together and communicate with each other according to the ABCF protocol or the QSIG protocol. Applications 20 and 22 respectively executed on the real time part of the interchange units 2 and 10 communicate via the line circuits 8 and 16 and the line 18. The figure is diagrammatic and shows only one line circuit in each interchange unit and one direct line between the two line circuits. Obviously a real configuration can be more complex than this schematic configuration.
The invention aims to solve the new problem of dialog between a mixed mode application in the mixed mode part of an interchange unit and a real time application in the real time part of a private interchange unit. Such dialog was neither provided for nor possible in the prior art interchange units.
To this end the invention proposes an application-oriented half-link which enables communication between real time and mixed mode applications.
To be more precise, the invention proposes an interchange unit for a private telecommunications network executing partly in real time and partly in mixed mode, which interchange unit includes a half-link which has an interface using a protocol used by the interchange unit for connecting real time applications to the outside and an application-oriented interface to at least one mixed mode application.
The protocol can be the QSIG protocol, for example.